package com.agan.net.nio;

import java.io.IOException;  
import java.net.InetSocketAddress;  
import java.net.ServerSocket;  
import java.nio.ByteBuffer;  
import java.nio.channels.SelectionKey;  
import java.nio.channels.Selector;  
import java.nio.channels.ServerSocketChannel;  
import java.nio.channels.SocketChannel;  
import java.util.Iterator;  
import java.util.Set;  
 
public class NIOServer {  
      
    /*标识数字*/ 
    private  int flag = 0;  
    /*缓冲区大小*/ 
    private  int BLOCK = 4096;  
    /*接受数据缓冲区*/ 
    private  ByteBuffer sendbuffer = ByteBuffer.allocate(BLOCK);  
    /*发送数据缓冲区*/ 
    private  ByteBuffer receivebuffer = ByteBuffer.allocate(BLOCK);  
    private  Selector selector;  
 
    public NIOServer(int port) throws IOException {  
        // 打开服务器套接字通道  
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();  
        // 服务器配置为非阻塞  
        serverSocketChannel.configureBlocking(false);  
        // 检索与此通道关联的服务器套接字  
        ServerSocket serverSocket = serverSocketChannel.socket();  
        // 进行服务的绑定  
        serverSocket.bind(new InetSocketAddress(port));  
        // 通过open()方法找到Selector  
        selector = Selector.open();  
        // 注册到selector，等待连接  
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);  
        System.out.println("Server Start----8888:");  
    }  
 
 
    // 监听  
    private void listen() throws IOException {  
        while (true) {  
            // 选择一组键，并且相应的通道已经打开  
            selector.select();  
            // 返回此选择器的已选择键集。  
            Set<SelectionKey> selectionKeys = selector.selectedKeys();  
            Iterator<SelectionKey> iterator = selectionKeys.iterator();  
            while (iterator.hasNext()) {          
                SelectionKey selectionKey = iterator.next();  
                iterator.remove();  
                handleKey(selectionKey);  
            }  
        }  
    }  
 
    // 处理请求  
    private void handleKey(SelectionKey selectionKey) throws IOException {  
        // 接受请求  
        ServerSocketChannel server = null;  
        SocketChannel client = null;  
        String receiveText;  
        String sendText;  
        int count=0;  
        // 测试此键的通道是否已准备好接受新的套接字连接。  
        if (selectionKey.isAcceptable()) {  
            // 返回为之创建此键的通道。  
            server = (ServerSocketChannel) selectionKey.channel();  
            // 接受到此通道套接字的连接。  
            // 此方法返回的套接字通道（如果有）将处于阻塞模式。  
            client = server.accept();  
            // 配置为非阻塞  
            client.configureBlocking(false);  
            // 注册到selector，等待连接  
            client.register(selector, SelectionKey.OP_READ);  
        } else if (selectionKey.isReadable()) {  
            // 返回为之创建此键的通道。  
            client = (SocketChannel) selectionKey.channel();  
            //将缓冲区清空以备下次读取  
            receivebuffer.clear();  
            //读取服务器发送来的数据到缓冲区中  
            count = client.read(receivebuffer);   
            if (count > 0) {  
                receiveText = new String( receivebuffer.array(),0,count);  
                System.out.println("服务器端接受客户端数据--:"+receiveText);  
                client.register(selector, SelectionKey.OP_WRITE);  
            }  
        } else if (selectionKey.isWritable()) {  
            //将缓冲区清空以备下次写入  
            sendbuffer.clear();  
            // 返回为之创建此键的通道。  
            client = (SocketChannel) selectionKey.channel();  
            sendText="message from server--" + flag++;  
            //向缓冲区中输入数据  
            sendbuffer.put(sendText.getBytes());  
             //将缓冲区各标志复位,因为向里面put了数据标志被改变要想从中读取数据发向服务器,就要复位  
            sendbuffer.flip();  
            //输出到通道  
            client.write(sendbuffer);  
            System.out.println("服务器端向客户端发送数据--："+sendText);  
            client.register(selector, SelectionKey.OP_READ);  
        }  
    }  
 
    /**  
     * @param args  
     * @throws IOException  
     */ 
    public static void main(String[] args) throws IOException {  
        // TODO Auto-generated method stub  
        int port = 8888;  
        NIOServer server = new NIOServer(port);  
        server.listen();  
    }  
} 
